Well-shaped fibre tips by pulling with a foil heater

The length of the molten zone determines the length of pulled optical fibre tips. Tips produced by laser or filament heating are rather lengthy. By using a foil heater the taper length can be shortened and cone angles in the order of 30 degrees can reproducibly be obtained. For varying the drawing force there is an optimum temperature range where the taper shape is monotonic for the whole tip. The tip end diameter is well below 100 nm for optimized pulling conditions.